With higher quality SLL light sources nowadays being readily available, it has become desirable to, instead of implementing lighting systems based on incandescent and fluorescent lighting technologies, utilize such SSL light sources for lighting in e.g. office spaces and in public areas such as department stores and airports. There are several reasons for SSL light sources being attractive as light source, based on inherent properties of solid state technology. For instance, SSL light sources provide for more energy-efficient lighting solutions.
Compared to the classical technologies of incandescent and fluorescent lighting, SSL devices such as Light Emitting Diodes and Organic Light Emitting Diodes (abbreviated LED and OLED, respectively) have different lighting characteristics, e.g. light quality of LEDs degrade with time in a way invisible to the eye of an observer, wherein in e.g. fluorescent lighting devices, for instance visible flickering, or part of the tube turning black, is a sign of the device being close to its end of operational life; the light quality is visibly lower than at the start of the light sources' life time. Incandescent light sources simply stop producing light.
For maintenance personnel of lighting systems in e.g. an office environment comprising a large amount of such SSL light sources, where each SSL light source may have been independently regulated and thereby each SSL light source having different burning hours to date, it thus becomes a non-trivial task to know which SSL light sources are to be replaced due to being close to its end of operational life and thus possessing a light quality below existing lighting norms. For example, automatic tuning of light output of lighting devices close to a window may have the consequence that these lighting devices can provide a different amount of burning hours compared to those lighting devices positioned away from windows. Different operating conditions as exemplified above render it more difficult for maintenance personnel to know when to change light sources.
Therefore, there is a risk that a light source is changed at a too early stage of its lifetime, making it both uneconomical and hazardous for the environment in the sense that the light source becomes waste disposal before its actual light quality is below e.g. lighting norms. Alternatively, a light source will not be changed in time, so that it will provide light below lighting norms, or even no light at all until maintenance personnel has been summoned to change the light source in the lighting device.
By replacing all SSL light sources simultaneously, light sources having a light quality below lighting standards may be reduced. However, as mentioned above, such an approach is not desirable, at least from an economical and environmental perspective.
It is known to implement software into an SSL light source, wherein after a predetermined amount of burning hours, the SSL light source starts to e.g. flicker, in order to model the behavior of for instance a fluorescent light source when reaching its end of life.
U.S. Pat. No. 7,425,798 discloses an intelligent degradation-sensing LED traffic signal. A signal can be sent through a communications port to notify that the LED is at the end of its useful life.